Effect pigments, also known as gloss or lustrous pigments, are well known as pigments that produce unique coloristic effects. The optical properties of effect pigments are governed by reflection and/or interference phenomenon. In particular, finishes containing an effect pigment produce a “flop effect” whereby the coloristic characteristics of the finish change depending on the viewing angle. In general, when a change in viewing angle results in a change in lightness, the effect is referred to as “lightness flop”, and when the change is in hue, the effect is referred to as “color flop”.
Due to their unique color characteristics, the market for effect pigments is growing in such uses as cosmetics, inks, plastics and paints, and especially automotive paints. Weather fast effect pigments are currently employed in large quantities in the automotive paint industry.
IR reflective pigments are known in the market, and are used in the military, construction, inks, plastics and coatings industries. Their demand is on the rise.
IR reflective inorganic pigments such as C.I. Pigment Black 30, a spinel formulated primarily with nickel, manganese, chrome and iron, and C.I. Pigment Green 17, a chromium green black hematite, have been known for many years and have become popular. Although some of these pigments possess high IR reflectance, they have drawbacks like low color strength, abrasiveness, and toxicity issues.
The literature also describes IR reflective organic pigments. In particular certain perylenetetracarboxylic acid diimide pigments show favorable IR reflection behavior when used as a black pigment or shading component for military camouflage and other purposes. Such perylenetetracarboxylic acid diimide pigments are described in the German Patents DE 24 51 780 B1 and DE 301 159 C.
German Patent DE 296 298 C describes dark green camouflage pigment mixtures comprising perylenetetracarboxylic acid-bis-N,N′-2-aminoethyl imide and/or 5,5-dichloro indigo.
U.S. Pat. No. 5,540,998 relates to a solar heat shielding coating composition which consists mainly of two or more of organic pigments selected from red, orange, yellow, green, blue and purple pigments in such a manner as to yield a color of low lightness, particularly achromatic black, by additive mixture in a weather resistant vehicle and a structure covered with said coating composition. The heat shielding coating composition is capable of covering the outside of said structure exposed directly to the sun and suppressing a rise in the inside temperature. Such selected composition shows a certain IR reflection and can be used for solar heat shielding. The use of C.I. Pigment Violet 29, a perylenetetracarboxylic acid diimide as a pigment component for such an application is not mentioned.
European Patent Application No.23,318 describes a gray to black colored thermoplastic film for laminated identity cards, containing a white pigment and/or filler and a gray mixture of colored organic pigments. Preferred materials are (A) antimony oxide, kaolin, silica, chalk, barium sulfate, titanium dioxide and zinc sulfide; (B) mixtures of red and green pigments in 6–12:10 weight ratio; violet and green in 5–15:10 weight ratio; and violet, yellow and blue in 20:30:10 to 50:60:10 weight ratio.
Copending U.S. patent application No. 60/367,180, published as WO03/080741, describes a black co-milled pigment composition comprising a mixture of from 2 to 98 parts by weight of a green halogenated copper phthalocyanine pigment and from 2 to 98 parts by weight of at least one second organic pigment that is not a green halogenated copper phthalocyanine pigment, and which pigment composition has a specific surface area below 50 m2/g. Such pigment compositions are different from those of the present invention. However, they have the disadvantage that a milling step is needed for their preparation. Additionally, they show different color shades when diluted with white, metallic or effect pigments.
The present invention relates to the surprising discovery that selected blends of a halogenated copper phthalocyanine with C.I. Pigment Violet 29, a perylenetetra-carboxylic acid diimide are black in masstone and can generate IR reflective colorations when applied in coatings, inks or plastics, and in particular, when applied together with effect pigments such as pearlescent mica.